1. Field of the Invention
The invention relates to a wrench, more particularly to an electronic torque wrench.
2. Description of the Related Art
U.S. Pat. Nos. 3,970,155, 4,006,629, 4,522,075, 4,669,319, and 4,976,133 disclose electronic torque wrenches that have strain gauges. The strain gauges detect elastic strains and changes in electrical resistances, translate the changes into an electrical signal, and in cooperation with a processing circuit which includes a Wheatstone bridge, an amplifier, a recorder, a microprocessor, an output unit, etc., determine a value of torque applied to a workpiece.
However, when the aforementioned electronic torque wrenches are used in a high electromagnetic interference (EMI) environment, such as in a heavily equipped factory, the accuracy of the electronic torque wrenches is adversely affected, and damage to electronic components inside the electronic torque wrenches may occur.